x11: Handle motif client message filter just like xdnd filters

gdk/x11/gdkdnd-x11.c

@@ -146,6 +146,8 @@ static const struct {
   const char *atom_name;
   GdkFilterFunc func;
 } xdnd_filters[] = {
+  { "_MOTIF_DRAG_AND_DROP_MESSAGE", motif_dnd_filter },
+
   { "XdndEnter",                    xdnd_enter_filter },
   { "XdndLeave",                    xdnd_leave_filter },
   { "XdndPosition",                 xdnd_position_filter },
@@ -3132,11 +3134,6 @@ _gdk_x11_display_init_dnd (GdkDisplay *display)
   int i;
   init_byte_order ();
 
-  gdk_display_add_client_message_filter (
-        display,
-        gdk_atom_intern_static_string ("_MOTIF_DRAG_AND_DROP_MESSAGE"),
-        motif_dnd_filter, NULL);
-
   for (i = 0; i < G_N_ELEMENTS (xdnd_filters); i++)
     {
       gdk_display_add_client_message_filter (